CN117626126A - 980MPa steel plate with thickness of 60-80mm and high strength and toughness and production method thereof - Google Patents
980MPa steel plate with thickness of 60-80mm and high strength and toughness and production method thereof Download PDFInfo
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- 239000010959 steel Substances 0.000 title claims abstract description 103
- 238000004519 manufacturing process Methods 0.000 title claims description 16
- 238000010791 quenching Methods 0.000 claims abstract description 42
- 230000000171 quenching effect Effects 0.000 claims abstract description 42
- 238000005496 tempering Methods 0.000 claims abstract description 34
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 9
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical compound OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 claims abstract description 6
- 239000000126 substance Substances 0.000 claims abstract description 5
- 238000012360 testing method Methods 0.000 claims abstract description 5
- 241000519995 Stachys sylvatica Species 0.000 claims abstract description 4
- 230000000149 penetrating effect Effects 0.000 claims abstract description 4
- 238000010438 heat treatment Methods 0.000 claims description 48
- 238000004321 preservation Methods 0.000 claims description 38
- 238000005096 rolling process Methods 0.000 claims description 33
- 238000009849 vacuum degassing Methods 0.000 claims description 28
- 238000001816 cooling Methods 0.000 claims description 25
- 238000005266 casting Methods 0.000 claims description 23
- 238000000034 method Methods 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 238000003723 Smelting Methods 0.000 claims description 10
- 238000007670 refining Methods 0.000 claims description 10
- 229910000851 Alloy steel Inorganic materials 0.000 claims description 6
- 239000002893 slag Substances 0.000 claims description 6
- 238000010079 rubber tapping Methods 0.000 claims description 5
- 229910045601 alloy Inorganic materials 0.000 claims description 4
- 239000000956 alloy Substances 0.000 claims description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- 238000007664 blowing Methods 0.000 claims description 4
- 230000006835 compression Effects 0.000 claims description 4
- 238000007906 compression Methods 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 239000001301 oxygen Substances 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 238000004925 denaturation Methods 0.000 claims description 2
- 230000036425 denaturation Effects 0.000 claims description 2
- 230000000717 retained effect Effects 0.000 claims 1
- 238000010008 shearing Methods 0.000 abstract 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 11
- 230000000694 effects Effects 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000011575 calcium Substances 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- 239000005997 Calcium carbide Substances 0.000 description 2
- 229910000616 Ferromanganese Inorganic materials 0.000 description 2
- 229910001309 Ferromolybdenum Inorganic materials 0.000 description 2
- 229910000628 Ferrovanadium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 description 2
- PNXOJQQRXBVKEX-UHFFFAOYSA-N iron vanadium Chemical compound [V].[Fe] PNXOJQQRXBVKEX-UHFFFAOYSA-N 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229910001562 pearlite Inorganic materials 0.000 description 2
- CLZWAWBPWVRRGI-UHFFFAOYSA-N tert-butyl 2-[2-[2-[2-[bis[2-[(2-methylpropan-2-yl)oxy]-2-oxoethyl]amino]-5-bromophenoxy]ethoxy]-4-methyl-n-[2-[(2-methylpropan-2-yl)oxy]-2-oxoethyl]anilino]acetate Chemical compound CC1=CC=C(N(CC(=O)OC(C)(C)C)CC(=O)OC(C)(C)C)C(OCCOC=2C(=CC=C(Br)C=2)N(CC(=O)OC(C)(C)C)CC(=O)OC(C)(C)C)=C1 CLZWAWBPWVRRGI-UHFFFAOYSA-N 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910000797 Ultra-high-strength steel Inorganic materials 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
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- 238000004904 shortening Methods 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
The invention discloses a 980MPa steel plate with 60-80mm thick and high strength and toughness, which comprises the following chemical components in percentage by mass (unit, wt%): c: 0.06-0.08, si:0.20 to 0.25, mn:0.60 to 0.70, P is less than or equal to 0.010, S is less than or equal to 0.002, ni:4.6 to 4.8, cr:0.5 to 0.6, mo:0.40 to 0.50, V:0.05 to 0.06 percent, and the rest is Fe and residual elements, after quenching and tempering, the structure is tempered sorbite and a small amount of residual austenite, the yield strength is 840 to 920MPa, the tensile strength is 940 to 1000MPa, the fracture elongation is more than or equal to 16 percent, the reduction of area is more than or equal to 50 percent, the impact power at minus 84 ℃ is more than or equal to 250J, the shearing section rate is more than or equal to 90 percent, the impact power at minus 100 ℃ is more than or equal to 200J, the shearing section rate is more than or equal to 80 percent, and the fracture part is fibrous after fracture test, and has no white spots, bright lines and penetrating split streamline. The comprehensive performance is good, and the quality requirement of 980MPa steel plate with high strength and toughness is completely met.
Description
Technical Field
The invention relates to the field of medium plate production, in particular to a steel plate with high strength and toughness and thickness of 60-80mm and 980MPa and a production method thereof.
Background
As is well known, low-carbon high-strength steel is one of the most important engineering structural materials, and is widely applied to projects such as petroleum and natural gas pipelines, ocean platforms, shipbuilding, large hydropower stations and the like. With the continuous forward development of metallurgical technology, people put forth higher requirements on the toughness, plasticity and welding performance of the ultra-high strength steel, namely, the steel plate has brittle fracture resistance and plastic instability fracture resistance at ultra-low temperature, and meanwhile, the fracture elongation and uniform elongation reach the level of 900 MPa-level tensile strength steel plate. In particular, in a deep sea working environment, the requirements on the high-pressure resistance and the low-temperature impact resistance of the steel plate are higher.
Patent document CN 113403551B discloses a method for manufacturing a high yield ratio hydrogen embrittlement resistant cold rolled DH980 steel plate, wherein the strength can reach more than 1000MPa after cold rolling and annealing, but the steel plate is too thin, belongs to the category of cold rolled steel, is not suitable for the field of medium and thick plate production, and the steel plate obtained by the scheme does not have low-temperature impact toughness.
Patent document CN 112143958B discloses a production method of a 1000 MPa-grade steel plate with super-thick, super-high toughness and excellent welding performance, wherein the tensile strength of the steel plate after quenching and tempering treatment reaches more than 950MPa, and the transverse Charpy impact energy at-60 ℃ reaches more than 100J, but still cannot meet the requirements of the use environment below-80 ℃. As the thickness of the steel sheet gradually increases, hardenability becomes worse and performance variability in the entire thickness direction of the steel sheet becomes larger, and the heat treatment technology disclosed in the patent literature cannot satisfy performance uniformity of the steel sheet in the entire thickness direction, and performance at the 1/2 position of the core is difficult to ensure.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims at providing a 980MPa steel plate with 60-80mm thickness and high strength and toughness; the second purpose of the invention is to provide a production method of a 980MPa steel plate with high strength and toughness and thickness of 60-80 mm.
The invention is realized by the following modes:
a980 MPa steel plate with thickness of 60-80mm and high strength and toughness comprises the following chemical components in percentage by weight: c: 0.06-0.08, si:0.20 to 0.25, mn:0.60 to 0.70, P is less than or equal to 0.010, S is less than or equal to 0.002, ni:4.6 to 4.8, cr:0.5 to 0.6, mo:0.40 to 0.50, V:0.05 to 0.06 percent, and the balance of Fe and residual elements.
In the composition design, the Ni element can reduce the critical cooling speed of the steel, improve the hardenability of the steel, enlarge the austenite region, be an effective element for austenitization, improve the strength of the steel, but not reduce the plasticity of the steel, and improve the low-temperature toughness of the steel. When Ni > 4.5% can prevent pearlite formation, can stabilize austenite, and martensitic transformation occurs at low temperature or in the as-cast state. However, too high Ni element can cause too strong hardenability to deteriorate toughness, so the content of Ni element is controlled to be 4.6% -4.8%;
the C element can improve the strength of the steel plate and increase the hardenability, but the excessive C content can affect the low-temperature impact toughness of the steel plate, and especially when the carbon content exceeds 0.10%, the number of small-angle grain boundaries in the steel can be increased, which is unfavorable for improving the impact toughness. The higher the C content is, the lower the section rate of the sheared fiber is, and the C content is controlled to be 0.06-0.08% on the premise that the high Ni steel has strong hardenability;
the Mo element is a ferrite forming element promoting, the hardenability of steel can be increased, meanwhile, the combination of the Mo element and the Ni element is more beneficial to preventing pearlite from being formed, but the excessive content of the Mo element further leads to the excessive hardenability so as to deteriorate toughness, so that the content of the Mo element is controlled to be 0.40% -0.50%.
Preferably, when the C content is 0.06% -0.07%, the Mn content is 0.65% -0.70%, the Cr content is 0.55% -0.60%, and the Mo content is 0.45% -0.50%; when the content of C is 0.071-0.08%, the content of Mn is 0.60-0.64%, the content of Cr is 0.50-0.54%, and the content of Mo is 0.40-0.44%. It should be noted that, in the limited element range, the content of the C element plays a critical role in the hardenability of the steel sheet, and when the content of the C element is low, the hardenability needs to be compensated by increasing the content of the Mn, cr, and Mo elements, and when the content of the C element is high, in order to avoid the phenomenon that the surface layer of the steel sheet is excessively quenched, which is unfavorable for low-temperature impact toughness, the content of the Mn, cr, and Mo elements needs to be reduced to balance the hardenability.
Further, the steel plate is in a quenched and tempered state, and the structure of the steel plate is tempered sorbite and a small amount of residual austenite; the yield strength is 840-920 MPa, the tensile strength is 940-1000 MPa, the elongation of fracture is more than or equal to 16%, the reduction of area is more than or equal to 50%, the impact power at-84 ℃ is more than or equal to 250J, the shear section rate is more than or equal to 90%, the impact power at-100 ℃ is more than or equal to 200J, the shear section rate is more than or equal to 80%, and the fracture is fibrous after fracture test, and has no white spots, bright lines and penetrating split streamline.
A production method of a 980MPa steel plate with 60-80mm thick and high strength and toughness comprises critical quenching, sub-temperature quenching and twice tempering, and specifically comprises the following steps:
a. and (3) critical quenching: the total heating time is 80-100 min, the heat preservation temperature is 830-850 ℃, the heat preservation time is 1.2min/mm, the quenching is carried out to room temperature after the furnace is taken out, the quenching water temperature is 18-25 ℃, and the quenching roller speed is 2.3m/min;
b. sub-temperature quenching: the total heating time is 80-100 min, the heat preservation temperature is 790-810 ℃, the heat preservation time is 1.0min/mm, the quenching is carried out to room temperature after the furnace is taken out, the quenching water temperature is 18-25 ℃, and the quenching roller speed is 2.3m/min;
c. primary tempering: the heat preservation temperature is set to 600-620 ℃, the tempering total coefficient is 3.5min/mm, and the water cooling is carried out to below 200 ℃ after the furnace is discharged;
d. and (3) secondary tempering: the heat preservation temperature is set to 620-640 ℃, the heating time is 60-80 min, the heat preservation time is 30-40 min, and the furnace is taken out for air cooling.
Preferably, when the C content is less than or equal to 0.07%, the temperature of the first tempering heat preservation stage is set to 600-610 ℃, and the temperature of the second tempering heat preservation stage is set to 620-630 ℃; when the C content is more than 0.07%, the temperature of the first tempering heat preservation stage is 611-620 ℃, and the temperature of the second tempering heat preservation stage is 631-640 ℃. It should be noted that, when the content of the element C is low, the hardenability of the steel sheet is slightly poor, and the tempering temperature needs to be lowered to ensure the strength of the steel sheet; when the content of the C element is higher, the hardenability of the steel plate is stronger, and the tempering temperature is required to be increased to ensure the low-temperature impact toughness of the steel plate, so that the effect of toughness matching is achieved.
What needs to be specifically stated is: 1. after critical quenching and sub-temperature quenching, austenite nucleation positions in steel are obviously increased, grain refinement effect is obvious, tempered sorbite with optimal obdurability matching effect is obtained after tempering, a small amount of residual austenite exists, the residual austenite can generate TRIP effect during mechanical property test, and stress induction martensite phase transformation is performed, so that the strength and toughness of the steel plate are improved; 2. the first tempering of the steel plate aims at fully converting the structure into tempered sorbite, cooling the steel plate to below 200 ℃ after discharging, avoiding the tempering brittleness interval of the steel plate, and the second tempering aims at improving the tempering temperature and shortening the tempering time due to the excessively strong hardenability of the surface layer of the steel plate, so that the surface layer is fully tempered and the strength of the central position of the steel plate is not reduced.
Further, the production method of the steel plate further comprises molten steel smelting, casting, steel ingot heating and rolling, and intermediate billet heating and rolling, and specifically comprises the following steps:
a. smelting molten steel: the converter adopts high alloy steel scraps as scrap steel, the alloy content in the scrap steel reaches Cr more than or equal to 1.0%, mo more than or equal to 0.5%, and Ni more than or equal to 1.5%; smelting by top-bottom re-blowing oxygen, wherein the content of C in converter tapping is less than or equal to 0.05%; adopting a process route of VD (vacuum degassing) C removal, LF refining and VD vacuum degassing, wherein after VD C removal, C:0.02-0.03%, wherein the white slag is made to adsorb the inclusions in the LF refining process, and simultaneously Ca wires are added to carry out denaturation treatment on the inclusions, H in molten steel after VD vacuum degassing is less than or equal to 1.0PPm, 25PPm and N are less than or equal to 23PPm;
b. casting: adopting a water-cooling ingot mould with the thickness of 800-840mm to cast, ensuring the compression ratio to be more than or equal to 10, the casting superheat degree to be 30-40 ℃, the body casting time to be 16-18 min, the riser casting time to be 6-8 min, and demoulding after casting for 10-12 h;
c. heating and rolling steel ingot: the steel ingot is stewed for 24-36h at the temperature of less than or equal to 500 ℃, is heated to 1160-1180 ℃ at the speed of less than or equal to 60 ℃/h and is insulated for 5h, is heated to 1180-1200 ℃ and is insulated for 5h, and finally is tapped and rolled to an intermediate billet with the thickness of 300mm after being insulated for 2h at 1160-1180 ℃;
d. heating and rolling an intermediate blank: heating the intermediate blank to 1180-1200 ℃, preserving heat for 5-7h, and preserving heat for 0.5-1.0h at 1160-1180 ℃; and after the heat preservation is finished, rolling to 140-160mm in the first stage, performing ACC controlled cooling after rolling, and starting to perform two-stage rolling to obtain a finished plate when the temperature returns to 820-860 ℃, wherein the final rolling temperature is 800-820 ℃, and performing ACC cooling again after rolling, wherein the final cooling temperature is less than or equal to 300 ℃.
The invention has the beneficial effects that: through reasonable design of steel plate components, control of the steel plate production process and precise control of the heat treatment process, the obtained steel plate has a structure of tempered sorbite and a small amount of residual austenite; the yield strength is 840-920 MPa, the tensile strength is 940-1000 MPa, the fracture elongation is more than or equal to 16%, the area shrinkage is more than or equal to 50%, the impact energy at-84 ℃ is more than or equal to 250J, the shear section rate is more than or equal to 90%, the impact energy at-100 ℃ is more than or equal to 200J, the shear section rate is more than or equal to 80%, the fracture is fibrous after fracture test, no white spots, bright lines and penetrating split streamline exist, the structure of the steel plate in the whole thickness direction is uniform, the performance is stable, and the performance attenuation degree along with the thickness direction is small.
Detailed Description
For a better understanding of the present invention, the following examples are set forth to further illustrate the invention, but are not to be construed as limiting the invention. In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the invention may be practiced without one or more of these details.
Example 1:
the chemical components (unit, wt%) of the following mass percentages are adopted: c:0.062, si:0.23, mn:0.68, P:0.004, S:0.001, ni:4.72, cr:0.57, mo:0.48, V:0.053, the others being Fe and residual elements.
a. Smelting molten steel: the converter adopts high alloy steel scraps as scrap steel, and the alloy content in the scrap steel reaches Cr:1.23%, mo:0.65%, ni:1.92%; top-bottom re-blowing oxygen smelting, wherein the content of C in converter tapping is 0.03%; adopting a process route of VD (vacuum degassing) C removal, LF refining and VD vacuum degassing, wherein after VD C removal, C:0.02 percent of LF refining process, aluminum particles and calcium carbide are added as molten steel deoxidizing agents, slag is required to turn white after slag formation, the heating time is controlled according to three times, the heating time is 15min, low-carbon ferromanganese is added, and the temperature of molten steel after heating is finished is 1575 ℃; adding ferrovanadium, nickel plates and ferromolybdenum in the second heating process, and preparing Cr, V, ni, mo element content according to the weight of molten steel, wherein the temperature of the molten steel reaches 1625 ℃ after the second heating is finished; and heating for 10min, and performing fine adjustment on the components of the molten steel alloy. Argon is blown from the bottom in the heating process, molten steel is stirred, impurities are adsorbed, and Ca wires are added to denature the impurities. And controlling the C content of the molten steel to be 0.06% after refining. H in molten steel after VD vacuum degassing: 0.82ppm,0:22PPm, N:20PPm;
b. casting: adopting a water-cooling ingot mould with the thickness of 820mm to cast, wherein the compression ratio is 10.2-13.6, the casting superheat degree is 35 ℃, the body casting time is 17min, the riser casting time is 8min, and demoulding is carried out 12h after casting;
c. heating and rolling steel ingot: the steel ingot is stewed for 30 hours at 460 ℃, the heating speed is 48.3 ℃/h, the temperature is kept for 5 hours at 1160-1180 ℃, the temperature is kept for 5 hours at 1180-1200 ℃ again, then tapping and rolling are carried out after the temperature is kept for 2 hours at 1160-1180 ℃, and the thickness of the intermediate billet is 300 mm;
d. heating and rolling an intermediate blank: the intermediate blank is heated at 1180-1200 ℃ for 6h, and then heated at 1160-1180 ℃ for 0.5h; the first stage rolling of the intermediate blank to 160mm thickness after heating, entering ACC for controlled cooling after rolling, starting two stages rolling to a finished plate when the temperature returns to 845 ℃, and entering ACC for cooling again after rolling at the final rolling temperature of 813 ℃ and the final cooling temperature of 260-280 ℃.
e. And (3) heat treatment: adopting a process of twice quenching and twice tempering, (1) critical quenching: the total heating time is 90min, the heat preservation temperature is 840 ℃, the heat preservation time is 1.2min/mm, the quenching is carried out to room temperature after the furnace is taken out, the quenching water temperature is 23 ℃, and the quenching roller speed is 2.3m/min; (2) sub-temperature quenching: the total heating time is 85min, the heat preservation temperature is 800 ℃, the heat preservation time is 1.0min/mm, the quenching is carried out to room temperature after the furnace is taken out, the quenching water temperature is 22 ℃, and the quenching roller speed is 2.3m/min; (3) primary tempering: the heat preservation temperature is set to 605 ℃, the total tempering coefficient is 3.5min/mm, and the water cooling is carried out to below 200 ℃ after the furnace is discharged; (4) and (3) secondary tempering: the heat preservation temperature is set to 625 ℃, the heating time is 70min, the heat preservation time is 35min, and the furnace is taken out for air cooling.
The mechanical properties are shown in Table 1:
TABLE 1 mechanical Properties
Example 2:
the chemical components (unit, wt%) of the following mass percentages are adopted: c:0.075, si:0.25, mn:0.62, P:0.005, S:0.001, ni:4.75, cr:0.52, mo:0.43, V:0.055, the others being Fe and residual elements.
a. Smelting molten steel: the converter adopts high alloy steel scraps as scrap steel, and the alloy content in the scrap steel reaches Cr:1.35%, mo:0.60%, ni:1.88%; top-bottom re-blowing oxygen smelting, wherein the content of C in converter tapping is 0.03%; adopting a process route of VD (vacuum degassing) C removal, LF refining and VD vacuum degassing, wherein after VD C removal, C:0.03 percent of LF refining process, adding aluminum particles and calcium carbide as molten steel deoxidizers, wherein slag is required to turn white after slag formation, heating time is controlled according to three times, heating time is 15min, low-carbon ferromanganese is added, and the temperature of molten steel after heating is finished is 1572 ℃; adding ferrovanadium, nickel plates and ferromolybdenum in the second heating process, and preparing Cr, V, ni, mo element content according to the weight of molten steel, wherein the temperature of the molten steel reaches 1628 ℃ after the second heating is finished; and heating for 12min, and performing fine adjustment on the components of the molten steel alloy. Argon is blown from the bottom in the heating process, molten steel is stirred, impurities are adsorbed, and Ca wires are added to denature the impurities. After refining, the C content of the molten steel is controlled to be 0.072%. H in molten steel after VD vacuum degassing: 0.9PPm,0:25PPm, N:22PPm;
b. casting: casting by adopting a water-cooling ingot mould with the thickness of 840mm, wherein the compression ratio is 10.5-14.0, the casting superheat degree is 33 ℃, the body casting time is 18min, the riser casting time is 7min, and demoulding is carried out 12h after casting;
c. heating and rolling steel ingot: the steel ingot is stewed for 36 hours at 450 ℃, the heating rate is 55 ℃/h, the temperature is kept for 5 hours at 1160-1180 ℃, the temperature is kept for 5 hours at 1180-1200 ℃ again, then steel is tapped and rolled after the temperature is kept for 2 hours at 1160-1180 ℃, and the thickness of the intermediate billet is 300 mm;
d. heating and rolling an intermediate blank: the intermediate blank is heated at 1180-1200 ℃ for 6.5h, and then heated at 1160-1180 ℃ for 0.5h; the first stage rolling of the intermediate blank to 160mm thickness after heating, entering ACC controlled cooling after rolling, starting two stages rolling to a finished plate when the temperature returns to 835 ℃, and entering ACC cooling again after rolling at the final rolling temperature of 810 ℃ and the final cooling temperature of 282-298 ℃.
e. And (3) heat treatment: adopting a process of twice quenching and twice tempering, (1) critical quenching: the total heating time is 95min, the heat preservation temperature is 840 ℃, the heat preservation time is 1.2min/mm, the quenching is carried out to room temperature after the furnace is taken out, the quenching water temperature is 22 ℃, and the quenching roller speed is 2.3m/min; (2) sub-temperature quenching: the total heating time is 90min, the heat preservation temperature is 800 ℃, the heat preservation time is 1.0min/mm, the quenching is carried out to room temperature after the furnace is taken out, the quenching water temperature is 23 ℃, and the quenching roller speed is 2.3m/min; (3) primary tempering: the heat preservation temperature is set to 615 ℃, the total tempering coefficient is 3.5min/mm, and the water cooling is carried out after the furnace is discharged to below 200 ℃; (4) and (3) secondary tempering: the heat preservation temperature is set to 635 ℃, the heating time is 65min, the heat preservation time is 35min, and the furnace is taken out and then air-cooled.
The mechanical properties are shown in Table 2:
table 22 mechanical properties
In conclusion, the 980MPa steel plate with the thickness of 60-80mm produced by the production method has remarkable effect, all the steps are matched with each other and synergistically increase, and the 60-80mm high-strength and high-toughness steel plate with excellent comprehensive performance is obtained.
Finally, it is noted that the above-mentioned embodiments are merely for illustrating the technical solution of the present invention, and that other modifications and equivalents thereof by those skilled in the art should be included in the scope of the claims of the present invention without departing from the spirit and scope of the technical solution of the present invention.
Claims (6)
1. A980 MPa steel plate with a thickness of 60-80mm and high strength and toughness is characterized by comprising the following chemical components in percentage by mass (unit, wt%): c: 0.06-0.08, si:0.20 to 0.25, mn:0.60 to 0.70, P is less than or equal to 0.010, S is less than or equal to 0.002, ni:4.6 to 4.8, cr:0.5 to 0.6, mo:0.40 to 0.50, V:0.05 to 0.06 percent, and the balance of Fe and residual elements.
2. The 980MPa steel sheet with high strength and toughness of 60-80mm thickness according to claim 1, wherein when the C content is 0.06% -0.07%, the Mn content is 0.65% -0.70%, the Cr content is 0.55% -0.60%, and the Mo content is 0.45% -0.50%; when the content of C is 0.071-0.08%, the content of Mn is 0.60-0.64%, the content of Cr is 0.50-0.54%, and the content of Mo is 0.40-0.44%.
3. The steel sheet of 980MPa with high strength and toughness and thickness of 60-80mm according to claim 1, wherein the steel sheet is in a tempered state and has a structure of tempered sorbite and a small amount of retained austenite; the yield strength is 840-920 MPa, the tensile strength is 940-1000 MPa, the elongation of fracture is more than or equal to 16%, the reduction of area is more than or equal to 50%, the impact power at-84 ℃ is more than or equal to 250J, the shear section rate is more than or equal to 90%, the impact power at-100 ℃ is more than or equal to 200J, the shear section rate is more than or equal to 80%, and the fracture is fibrous after fracture test, and has no white spots, bright lines and penetrating split streamline.
4. A method for producing a steel sheet with a thickness of 60-80mm and a high strength and toughness of 980MPa according to claim 1 or 3, wherein the steel sheet comprises critical quenching, sub-temperature quenching and two tempering steps, specifically comprising:
a. and (3) critical quenching: the total heating time is 80-100 min, the heat preservation temperature is 830-850 ℃, the heat preservation time is 1.2min/mm, the quenching is carried out to room temperature after the furnace is taken out, the quenching water temperature is 18-25 ℃, and the quenching roller speed is 2.3m/min;
b. sub-temperature quenching: the total heating time is 80-100 min, the heat preservation temperature is 790-810 ℃, the heat preservation time is 1.0min/mm, the quenching is carried out to room temperature after the furnace is taken out, the quenching water temperature is 18-25 ℃, and the quenching roller speed is 2.3m/min;
c. primary tempering: the heat preservation temperature is set to 600-620 ℃, the total tempering time is 3.5min/mm, and the water cooling is carried out to below 200 ℃ after the furnace is discharged;
d. and (3) secondary tempering: the heat preservation temperature is set to 620-640 ℃, the heating time is 60-80 min, the heat preservation time is 30-40 min, and the furnace is taken out for air cooling.
5. The method for producing a 980MPa steel plate with high strength and toughness and 60-80mm thickness according to claim 4, wherein when the C content is less than or equal to 0.07%, the temperature of the first tempering heat preservation stage is set to 600-610 ℃ and the temperature of the second tempering heat preservation stage is set to 620-630 ℃; when the C content is more than 0.07%, the temperature of the first tempering heat preservation stage is 611-620 ℃, and the temperature of the second tempering heat preservation stage is 631-640 ℃.
6. The method for producing a 980MPa steel sheet with high strength and toughness of 60-80mm thickness according to claim 4, wherein the steel sheet production method further comprises molten steel smelting, casting, steel ingot heating and rolling, intermediate billet heating and rolling, specifically comprising the steps of:
a. smelting molten steel: the converter adopts high alloy steel scraps as scrap steel, the alloy content in the scrap steel reaches Cr more than or equal to 1.0%, mo more than or equal to 0.5%, and Ni more than or equal to 1.5%; smelting by top-bottom re-blowing oxygen, wherein the content of C in converter tapping is less than or equal to 0.05%; adopting a process route of VD (vacuum degassing) C removal, LF refining and VD vacuum degassing, wherein after VD C removal, C:0.02-0.03%, wherein the white slag is made to adsorb the inclusions in the LF refining process, and simultaneously Ca wires are added to carry out denaturation treatment on the inclusions, H in molten steel after VD vacuum degassing is less than or equal to 1.0PPm, 25PPm and N are less than or equal to 23PPm;
b. casting: adopting a water-cooling ingot mould with the thickness of 800-840mm to cast, ensuring the compression ratio to be more than or equal to 10, the casting superheat degree to be 30-40 ℃, the body casting time to be 16-18 min, the riser casting time to be 6-8 min, and demoulding after casting for 10-12 h;
c. heating and rolling steel ingot: the steel ingot is stewed for 24-36h at the temperature of less than or equal to 500 ℃, is heated to 1160-1180 ℃ at the speed of less than or equal to 60 ℃/h and is insulated for 5h, is heated to 1180-1200 ℃ and is insulated for 5h, and finally is tapped and rolled to an intermediate billet with the thickness of 300mm after being insulated for 2h at 1160-1180 ℃;
d. heating and rolling an intermediate blank: heating the intermediate blank to 1180-1200 ℃, preserving heat for 5-7h, and preserving heat for 0.5-1.0h at 1160-1180 ℃; and after the heat preservation is finished, rolling to 140-160mm in the first stage, performing ACC controlled cooling after rolling, and starting to perform two-stage rolling to obtain a finished plate when the temperature returns to 820-860 ℃, wherein the final rolling temperature is 800-820 ℃, and performing ACC cooling again after rolling, wherein the final cooling temperature is less than or equal to 300 ℃.
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